A full binary tree (a.k.a. proper binary tree or 2-tree) is a tree in which every node other than the leaves has two children

a.If the level of the root of a non-empty full binary tree is level 0, the level of the root's children is level 1, etc., how many nodes are on level i, i 1?

b.If a non-empty full binary tree has n levels, how many nodes does the tree have in total?